The present invention relates to a syringe for dispensing viscous materials, comprising an outlet member and a plunger means for dispensing the material from the syringe whereby the dispensing means can be at least partly inserted into the outlet member.
Such a syringe is, for example, known from U.S. Pat. No. 3,900,954.
This syringe is characterized by an especially good utilization of the dental material to be applied. The syringe comprises a dispensing body at the forward end of the plunger of the syringe. the dispensing body has a conically tapering tip which can be introduced into the outlet member so as to displace the dental material as completely as possible.
With such a dispensing body it is possible to reduce the amount of dental material that would otherwise remain within the syringe. However, some material is always retained within the outlet member so that the dental material within the syringe which is, in general, an expensive product, cannot be completely utilized. For example, when a light-curing dental material is used, the dental material over time will cure within the syringe and will plug the outlet member.
In order to prevent such losses of dental material, it has been suggested to shorten the dispensing body and to make it more compact. Since such a syringe is used for applying the filling material in the mouth of a patient, such a construction, however, leads to the problem that not all teeth can be easily reached with the syringe.
For example, from British Patent 298 292 it is known to use a very short and thin outlet member into which a special end piece of the plunger which is comprised of rubber can be introduced. This solution, however, allows only for a comparatively minimal dispensing velocity and the pressure applied onto the viscous material increases with reduction of the flow cross-section of the outlet member. Furthermore, the actuating force due to the friction of the rubber plunger is relatively great, since the plunger is slightly larger than the inner diameter of the housing in order to provide the necessary sealing action. It is not surprising that such rubber plungers have not found ac ceptanoe in practice.
Especially when the outlet member is positioned at an angle relative to the axis of the syringe, the guiding of the dispensing body within the outlet member is unsatisfactory. The forward end is relatively freely movable and has the tendency to cling to a wall when pressure is applied by the plunger. Due to the asymmetric guiding of the dispensing body there is the risk that the dental material can exit laterally relative to the dispensing body. This can result in a soiling of the syringe.
It is therefore an object of the present invention to provide a syringe for viscous materials according to the aforementioned kind and/or a method for manufacturing such a syringe that allows for a reliable and complete dispensing of the used viscous material, especially a dental material.